Method and apparatus for the manufacture of reinforcing bars



' June 1, 1965 .LGILLBERG 3,1 ,2 5

METHOD AND APPARATUS FOR THE MANUFACTURE OF REINFORCING BARS Filed June 19,, 1961 '4 sneets-shaet 1 June 1, 1965 J. GILLBERG 3, 5

METHOD AND APPARATUS FOR THE MANUFACTURE OF REINFORCING BARS Filed June 19, 1961 4 Sheets-Sheet 2 4 Sheets-Sheet 3 INVENTOR MINA/55 swam,

y mun ATTORNEYS J. GILLBERG METHOD AND APPARATUS FOR THE MANUFACTURE OF REINFORCING BARS Filed June 19, 1961 June 1, 1965 June 1, 1965 r J. GILLBERG 3,186,206

METHOD AND APPARATUS FOR THE MANUFACTURE OF REINFORCING BARS Filed June 19, 1961 4 Sheet s-Sheet 4 INVENTOR JOf/fl/V/VAKS 6am,

ATTORNEYS United States Patent 3,186,206 METHOD AND APPARATUS FGR THE MANU- FACTURE 0F REINFURKIING BARS Johannes Gillberg, Sveagvagen 1'22, Stockholm, Sweden Filed June 19, 1961, Ser. No. 118,137 Claims priority, application Germany, June 21, 1959, G 29,905 3 Claims. (Cl. 72-194) Thisinvention relates to the manufacture of reinforcing bars for concrete structures, which bars have alternating impressions and projections on the surface which enhance the anchoring and the ability of adherence to the concrete as compared with smooth reinforcing bars. Due to the effective anchoring of the bars in the concrete, normally no special anchoring hooks need be provided at the ends of the bars which saves material and work. Conventional reinforcing bars of this type are manufactured by hot rolling of steel which usually has a carbon content of about 0.30%, the steel being alloyed to insure the required strength properties.

The object of the invention is to produce a reinforcing bar from a less expensive initial material with a lower carbon content .by cold working, which bar as regards quality and elfectivity is equivalent to a reinforcing bar made directly from a high-grade material by red hot rolling. In the development of the novel method regard has been paid especially to the possibility of using an initial material, namely a rolled rod, which in the manufacture in the steelworks is produced in the form of coils and consequently can be readily shipped and stored. The novel method also renders possible a continuous refiningtreatment of the steel without interruptions, which treatment can be performed in a continuously operating apparatus.

In its broadest aspect the method according to the invention is characterized by pulling a steel bar preferably circular in cross-section by means of one or more pairs of drive rolls between stamp disks which are driven by the steel bar and cold-form the bar by compressing the material of the bar so as to make impressions therein between which projections are formed which enhance the anchoring and ability of adherence of the bar to the concrete.

For reasons to be explained later on it is important to form the impressions in the bar with high accuracy so that the desired shape of the impressions is maintained in operation as far as possible. This requirement cannot be satisfied if the dies of the stamp disks also are used to move forward the steel bar, since the dies in such case would have an adverse effect inter alia upon the edges of the impressions in the bar.

It is also highly important that the reinforcing bar provided with the impressions should leave the stamping device in a straightened form, this being a problem in so far as the rolled rod is furnished in a coiled state. The steel bar can be straightened in a simple manner if it is advanced by means of two cooperating drive rolls provided with dogs adapted to be alternately urged against the bar such that the bar in addition to the impressions produced by the stamp disks is provided with marks made by the dogs, said marks being located alternately on opposite sides of the bar. Such straightening drive rolls are known per se. As viewed in the direction of feed they should be located behind the stamp disks. As a result, the steel bar leaving the drive ro-lls has been straightened and can be cut into predetermined lengths by automatically operating means.

It is especially advantageous if the marks impressed by the dogs are groove-shaped and extend at an oblique angle to a plane perpendicular to the longitudinal axis of the bar.

The marks located on the same side of the bar are preferably alternately impressed in opposite oblique directions with reference to a plane located between the marks.

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The initial material which preferably is an unalloyed low-carbon steel should be treated, in accordance with the invention, by the cold-forming action of the stamp disks so as to satisfy the demands on the finished reinforcing bar, namely, improved yield limit, the so-called 0.2% strain, required ultimate strength, a certain ultimate elongation, and improved adherence to the concrete by suitable dimensions of the depths and the mutual distance of the impressions. Further, the drive rolls'should be able to straighten the reinforcing bar. The yield limit and the ultimate strength should be improved to such an extent by the cold-forming operation as compared with the initial material as to correspond substantially, to the properties of a conventional ribbed bar which in this respect has permissible values for the use in consideration. This object is attained by a comparatively forcible compression and simultaneous elongation of the initial material. However, the cold-working operation should be such that the ultimate elongation which initially is very high, for instance about 25% in the mild steel, will not be lowered below about 8%.

.For instance, the cold-Working of the rolled rod by means of the stamp disks may result in an increase of the initial yield limit of about 28 kg./rnm. to more than 42 kg./mm. the elongation of the steel resulting from the stamping action being between 6% and 10%, for instance about 8%. At the same time the ultimate strength is antomatically increased to more than 50 kg./mm.

With an initial material having a diameter of between 5 mm. and 13 mm., that is, withinthe range which in the first place 'is concerned with the invention, the following specifications are examples of the above-named improve ments in quality. The depths of the impressions are such that the difference in height between the impressions and the intermediate projections, as viewed in a longitudinal section of the steel bar,,amounts to between 0.041! and 0.1503, preferably between 0.05d and 0.111, for instance 0.08:1, d being the diameter of the steel bar. Further, the ratio of the dimensions of the impressions longitudinally of the steel bar to the dimensions of the projections is between 0.7:1 and 1:0.7, for instance about 1:1. The mutual distance between the impressions disposed in a longitudinally extending row is suitably between 0.7d and 1.4d and preferably about equal to d which again is the diameter of the steel bar.

The impressions resulting in a compression of the material are disposed in two or more longitudinally extending rows and are symmetric with respect to a plane through the longitudinal axis of the steel bar. Preferably,

.the rows of impressions are provided in an even number,

such as two or preferably four and possibly six or more rows such that they can be disposed in pairs diametrically opposite each other. The rows may be arranged such as to leave between themselves non-impressed intermediate longitudinal parts, in which case the marks impressed by the dogs are disposed at least along part of their length at two of such diametrically opposite intermediate parts.

A particularly high endurance strength is required for reinforcing bars to be used in dynamic structures. It has been proved that the endurance strength can be considerably increased if the impressions and projections as well as their boundary edges formed by the stamp disks, as viewed laterally of the steel bar, extend at an oblique angle to a plane perpendicular to the longitudinal axis of the bar. The same holds true of the marks impressed by the dogs. It also has been proved that sharp stamped edges and corners must be avoided. Accordingly, the obliquely extending impressions are shaped in such a manner that they form outwardly extending boundary edges only together with the intermediate projections, that is, at the places where these edges are of importance to the anchoring of the reinforcing bar to the concrete. These edges merge into the substantially flat bottom of the impressions via a well rounded fillet the radius of curvature of which may be about of the diameter of the bar. As viewed in a longitudinal section through an impression and the adjacent projection, the edges are inclined outwardly from the bottom at an angle of 10 to 45 preferably 30. To prevent the formation of impressed corners, the impressions have substantially fiat bottoms as viewed in cross-section. From this it follows that the depth of the impressions as viewed in cross-section is zero at the beginning and at the end of the impression so that no corners can be formed. This is of great consequence to the increase of the endurance strength.

The initial material is an unalloyed carbon steel with a carbon content of between 0.05% and 0.25%, preferably between 0.10% and 0.20%.

The invention also relates to an apparatus for carrying into effect the method. The apparatus is described below with reference to an embodiment illustrated in the annexed drawing. In connection therewith, the method and the reinforcing bar manufactured in accordance therewith will be explained more closely.

FIG. 1 illustrates, partly quite diagrammatically, a lateral elevation of a stamping device and a feed device. FIG. 2 shows an example of the mounting of the stamp disks as viewed in the direction of the arrows IIII in FIG. 1. FIG. 3 illustrates a detail. FIG. 4 is a lateral view of a reinforcing bar manufactured in accordance with the invention, and FIG. 5 shows the bar as viewed from the left in FIG. 4. FIGS. 6 and 7 are corresponding views a -of a second embodiment.

FIG. 8 is an enlarged crosssectional view of the bar on line VIIIVIII of FIG. 4. FIG. 9 is a sectional view along the line IXIX of FIG. 8. FIG. 10 is a view similar to that in FIG. 2 but on a smaller scale showing the means for applying'pressure to the stamp disks and FIG. 11 is a vertical section, partly in elevation, in a plane through the axes of the shafts 31 and 32 of FIG. 1.

In FIG. 1 numeral 10 denotes a rolled steel bar with a carbon content of about 0.20% which is pulled in the direction of the arrow p by means of drive rolls 1 and 1a provided with dogs 2. The stock of the bar is initially coiled on a supply reel (not shown) and is pulled through a stamping device 11 diagrammatically illustrated in FIG. 1. FIG. 2 shows an example of a stamping device viewed longitudinally of the steel bar. The bar is moved along centrally of FIG. 2 between the stamp disks 12, 13, and

- 14, 15 which make the impressions in the bar that compress and elongate the material, the main cold-working of the steel being performed at this place. The disks are freely rotatably mounted on shafts 16 so as to be rotated due to their engagement with the steel bar.

The number of stamp disks may vary. Preferably, one or more pairs of stamp disks are disposed in opposite relationship, two pairs being illustrated in the embodiment. The bar is worked simultaneously by all of the disks substantially at the same section of the bar. Instead thereof the pairs of disks may be displaced relative to each other longitudinally of the bar.

By means of carriers 17 the shafts 16 are in pairs pivotally mounted on shafts 18 and 19 which are stationarily mounted in the frame of the apparatus and extend longitudinally of the steel bar. Due to this arrangement, the disks are adjustable towards and away from the steel bar. The disks are subjected to forces which correspond to :the desired depth of the impressions and consequently to the desired cold-forming action. These forces can be varied during operation. In the embodiment illustrated the forces act upon the shafts 16 in the directions of the arrows p in FIG. 2. As shown in FIG. 10, the forces are produced by springs 42, 43, mounted in a frame 41 constructed such that the force is uniformly distributed to all of the stamp disks 12-15. The frame 41 comprises vertical, longitudinal bars 44 rigidly connected to cross bars 45 and 46. On the ba s 44 there are slidably the finally stamped bar.

mounted upper and lower cross members 47 and 48. Each of these members 47 and 48 has a cavity 49 in which a head 50 is rockably mounted. On either side of the center line through said heads 50 there are cavities 51 and in each cavity rests one end of a pin 112, 113, 114, 115, the other ends of the pins abutting a shaft 16 of the stamp disks 12, 13, 14 and 15.

From the drawing it will be evident that the springs 42, 43, on the one hand abutting the slidable cross members 47 and 48 and on the other hand the cross bars 45, 46 will urge the shafts l6 and, thus, the disks 12, 13, 14 and 15 against the steel bar moving along the center of the stamping device.

I11 order to adjust the forces of the disks 12-15 against the steel bar, the upper end of the upper spring 42 does not contact the cross bar 45 directly but abut-s a pan 52 which is connected to the cross bar 45 by means of a screw 53 screwed through the cross bar.

When the spring 42 is compressed by means of the screw 53 in order to adjust the pressure exerted on the stamp disks, the increased pressure of the spring 42 will be transmitted to the spring 43 by means of the cross bar 45, the bars 44, and the cross bar 46.

The frame 41 is held in position and supported by the shafts 16 and thus also by means of the shafts 18 and 19 mounted in the frame 56 of the apparatus. Furthermore, the pins 112-115 are guided in the frame 56.

The disks 12-15 have circular stamping rims 12a-15a with stamping dies which in accordance with the desired peripheral extension of the impressions extend along corresponding parts of the circumference and the mutual distance of which corresponds to the dimension of the projections to be formed on the bar. In the embodiment illustrated, the stamp dies extend obliquely at an angle of about 45 with respect to the axis of the disk, but other angles may be chosen. The dies or projections are consequently in the form of oblique-angled parallelograms and should have an axial extension which is greater than the cord which as viewed in a cross-section is formed by the impression in the bar.

The shape and arrangement of the stamp dies will be apparent from FIGS. 4 to 9 which illustrate examples of In accordance with the stamping rims 12a-15a in FIG. 2 the impressions are marked 012a, 013a, 014a, 015a. The projections between the impressions are marked 20. The impressions and projections are disposed in parallel rows along the bar, the arrangement being such that non-impressed intermediate longitudinal parts 21, 21 and 22, 22 are left between the rows, said parts being located diametrically opposite each other. As will be seen from FIG. 2, the angles between the disks 12-15 are such that the intermediate parts 22 will be wider than the intermediate parts 21. For this reason, the marks 01 and 01a impressed by the dogs 2 of the drive rolls 1 and 1a are preferably provided in the wider intermediate parts 22.

At the places where the impressions 012a-015a merge into the projections 20 there are formed edges 23 which act as teeth for enhancement of the anchoring of the bar. No other transition edges are formed by the impressions, since the bottom of each impression merges directly into the initial circumference of the steel bar at 24 (FIG. 8). The form of the impressions in a longitudinal section of the bar is illustrated in FIG. 9.

FIGS. 4 and 5 illustrate a reinforcing bar which has been formed by means of stamp disks with oblique stamp dies in accordance with FIG. 2. The directions of the edges 23 are different in adjacent rows of impressions which assists in preventing the bar from turning about its own axis during the stamping operation. In the embodiment shown in FIGS. 6 and 7 the impressions have other mutual directions.

The rings which constitute the stamping rims 12a-15a in FIG. 2 are preferably exchangeable and are inserted between plates 25 which form a rotor mounted on the shaft 16. Since the stamp disks are individually rotatable, the rows of impressions may be displaced relative to each other longitudinally of the bar, but this is scarcely a disadvantage. On the contrary it is of great importance that the stamp disks be not coupled with each other in a manner such that they cannot freely roll along the bar during the stamping operation and that sliding movements occur between the disks and the her.

As shown in FIGS. 4 and 6, the marks 01 and 01a impressed by the dogs extend preferably at an oblique angle to a cross-section of the bar. Since the same holds true of the impressions, the result is an increased endurance strength. The oblique direction of the marks impressed by the dogs is due to the fact that the dogs 2 of the drive rolls 1 and 1a extend in correspondingly oblique directions with respect to planes through the axis of rotation. In order to prevent the steel bar from being turned in one direction as a result of the oblique directions of the marks impressed by the dogs, the dogs 2 extend alternately in opposite directions.

A suitable construction and arrangement of the dogs 2 of the drive roll 1 and 1a is shown in FIG. 3. The body 30 of each drive roll is preferably keyed on to the shaft 31 or 32 and has a peripheral groove 33 the open end of which is suitably slightly wider than the diameter of the actual reinforcing bar. Spaced bores 34 extend through parts of the groove 33, and loosely inserted into said bores are the dogs 2 which are made from hardened round bar steel or cemented carbide. The dogs are axially mounted such as by means of lateral disks 35 which areb olted to the body 30. In operation, the steel dogs 2 can rotate in the bores so that wear will be distributed along the entire circumference. As will be apparent the marks impressed upon the reinforcing bar by means of the dogs 2 will have a smoothly rounded form longitudinally of the bar, this being important in so far as the formation of cracks in the reinforcing bar will be prevented.

From FIG. 3 it will further be seen that the reinforcing bar as it passes between the drive rolls under the action of the dogs 2 will not extend down to the bottom of the groove 33. Consequently, the bar will be gripped only at the places where the marks are to be impressed. When a dog 2 is impressing a mark, the bar rests at a place in front of and at a place behind this dog on a dog 2 on the opposite side of the bar.

Due to the alternating engagement of the dogs on opposite sides of the steel bar, the bar will be straightened. The drive rolls 1 and 1a consequently act as feed means as well as straightening means. In addition, the anchoring surface of the bar in the concrete is increased by the marks impressed by the dogs. The dogs also perform a certain cold strengthening of the bar. The pressure exerted "by the dogs 2 and the resulting depth of the marks impressed by the dogs in the bar is mainly determined by the traction required for moving the steel bar between V the stamp disks.

One or both of the drive rolls 1, in may be displaceable towards the other one for varying the pressure exerted on the bar. Further, the drive rolls may be circumferentially displaceable relative to each other for varying the straightening action on the bar, which may be performed in different ways.

For instance referring to FIG. 11 the two shafts 31 and 32, carrying the drive rolls 1 and 1a, respectively, are rotatably mounted in the frame 56 of the device. Secured to each shaft there is a gear, 57 and 58, respectively, the teeth of which extend obliquely to the axes of the shafts. The teeth of the gear 53 mesh with the teeth of a gear 39 fastened to a drive shaft 69 which is positively driven by means of a gear 61 driven by a source of power (not shown). Two pinions 63 and 64 made in one piece are mounted freely rotatable on ashaft 65. The shaft 65 is 'displaceable in its longitudinal direction by means of a screw 66 fastened to the shaft and screwedin the frame 56.

The teeth of the pinion 63 mesh with the teeth of the gear 57 associated with the drive roll 1 and the'teeth of the pinion ea engage the teeth of the gear 59 which by means of the gear 58 is associated with the drive roll 1a. The teeth of the gear 57 and the teeth of the gear 59 extend obliquely in opposite directions. Thus, upon displacement of the pinion 63 in a longitudinal direction to the shaft 65, the two drive rolls, 1 and 1a, will be given a displacement in opposite directions relative to the steel bar advanced between the said rolls. This relative displacement is dependent on the distance to which the shaft 65 is displaced.

What I claim is:

1. Apparatus for making reinforcing bars comprising at least one pair of oppositely disposed cooperating circular and freely rotatable stamp disks adapted to be urged against a steel bar passing therebetween, each stamp disk having circumferentially spaced apart radially protruding stamp dies adapted to engage said bar and form impressions therein, said dies extending obliquely to the circumferences of said disks and said disks being each independently mounted and a feed device positioned behind said stamp disks for pulling a steel bar between said stamp disks, said feed device comprising two oppositely disposed drive rolls having spaced apart peripheral rounded obliquely extending dogs adapted to engage said bar and said rolls being coupled to be dri en at the same peripheral speed.

2. Apparatus as defined in claim 1 comprising means for adjusting the drive rolls circumferentially with respect to each other and said rounded dogs being rotatably supported by said drive rolls.

3. Apparatus as defined in claim 1 comprising at least two pairs of stamp disks, each of said disks being mounted for rotation on a first shaft that is pivotally mounted at one end on a second shaft that is parallel to the direction of movement of bar and means for urging the free end of each of said first shafts toward the path of said bar, the axes of rotation of all of said disks being in the same plane perpendicular to said path.

References Cited by the Examiner UNITED STATES PATENTS 665,473 1/01 Savery 56 1,378,860 5/21 Heinle 8063 1,968,670 7/34 Carroll 80-63 2,027,283 1/36 McFadden 80-56 2,327,103 8/43 Gude 803 2,377,980 6/45 Surerus 50528 2,552,364 5/51 Bradbury 50528 2,811,882 11/57 Hess 80-63 2,870,626 l/59 Gillsberg 8063 FOREIGN PATENTS 820,703 9/59 Great Britainr CHARLES W. LANI-IAM, Primary Examiner.

LEON PEAR, Examiner. 

1. APPARATUS FOR MAKING REINFORCING BARS COMPRISING AT LEAST ONE PAIR OF OPPOSITELY DISPOSED COOPERATING CIRCULAR AND FREELY ROTATABLE STAMP DISKS ADAPTED TO BE URGED AGAINST A STEEL BAR PASSING THEREBETWEEN, EACH STAMP DISK HAVING CIRCUMFERENTIALLY SPACED APART RADIALLY PROTRUDING STAMP DIES ADAPTED TO ENGAGE SAID BAR AND FORM IMPRESSIONS THEREIN, SAID DIES EXTENDING OBLIQUELY TO THE CIRCUMFERENCES OF SAID DISKS AND SAID DISKS BEING EACH INDEPENDENTLY MOUNTED AND A FEED DEVICE POSITIONED BEHIND SAID STAMP DISKS FOR PULLING A STEEL BAR BETWEEN SAID STAMP DISKS, SAID FEED DEVICE COMPRISING TWO OPPOSITELY DISPOSED DRIVE ROLLS HAVING SPACED APART PERIPHERAL ROUNDED OBLIQUELY EXTENDING DOGS ADAPTED TO ENGAGE SAID 